1. Field of the Invention
This invention relates to a method for fabricating a laminated magnetic head and, more particularly, to a method for fabricating a magnetic head for improving product yield during machining of core blocks by increasing a bonding force between substrates and laminated magnetic film.
2. Background of the Invention
Video cassette recorders (VCRs) for broadcasting as well as for home use require recordings having high picture quality and high density. Accordingly, magnetic heads for high picture quality VCRs for S-VHS and HDTV in the market use alloy magnetic films of sendust amorphous Fe-Al series alloys and Co-Ta-Zr alloy having a high saturated magnetic flux density deposited on a ferrite or a non-magnetic ceramic substrate. Therefore, the magnetic head employing such an alloy magnetic film can operate with a metal tape having a high coercive magnetic force.
However, in general, such an alloy magnetic material prevents high frequency magnetic field from penetrating deep into the depths of the core and the high frequency magnetic field concentrates on the surface due to a low electric resistance of the alloy magnetic material. That is, a problem of low magnetic permeability exists due to a development of an eddy current. Such a problem is solved by laminating alloy magnetic films and non-magnetic material alternately.
FIGS. 1A, 1A', 1B and 1C show a laminated magnetic head, presently in use, formed from using the foregoing method. The laminated magnetic head includes a laminated magnetic film 4 having soft magnetic alloy films 2 and insulation films 3 of SiO.sub.2 laminated alternately on a non-magnetic substrate 1a, and a substrate 1b bonded to the substrate 1a, formed through the above process with bonding glass 5. Reference number 7 is a gap and reference number 6 is glass.
FIGS. 2A to 2K illustrate processes for fabricating the magnetic head. The laminated magnetic film 4 is formed by laminating the soft magnetic alloy films 2 and the insulation films 3 alternately to a thickness of a track width on a non-magnetic substrate as shown in FIG. 2A, both sides of which have been lapped or polished. A thin film of bonding glass 5 is coated on the other side of the lamination, as shown in FIGS. 2B and 2C.
A plurality of the substrates formed through the foregoing process are stacked, as shown in FIGS. 2D and 2E, bonded at high temperature, cut, and ground to form a plurality of core blocks, as shown in FIG. 2F. Next, as shown in FIG. 2G, a winding groove 8 and a reinforcement groove 9 for inserting glass are formed in a C-core block, and glass filling grooves 10 for strengthening the bonding force when bonding with the C-core block are formed in an I-core block.
Then, tracks of the I-core and the C-core blocks are matched and bonded by placing the surface faces 11 and 11' of the I-core and the C-core blocks respectively together with non-magnetic material, such as SiO.sub.2, deposited to form a gap length on the surface faces 11 and 11' of the I-core and C-core blocks, respectively. As shown in FIG. 2H, glass bars are inserted into the winding groove 8 and the glass reinforcement groove 12, which are subjected to a high temperature heat treatment for melting and bonding to obtain a glass bonded bar.
Subsequently, by forming outside winding grooves (FIG. 2I), Carrying out R grinding 13 and step grinding 14 of the sliding surface to improve contact with the tape (FIG. 2J), and cutting along dotted lines A-A' and B-B', the magnetic head core chips, shown in FIG. 1 and 2K, can be obtained.
However, in the foregoing conventional fabrication method, the bonding force becomes weak due to a difference in the thermal expansion coefficient for one another and affinity for the substrate, for example, when the bonding glass between the laminated magnetic film 4 and the non-magnetic substrate 1b is bonding.
Accordingly, substrate 1b can fall from the laminated magnetic film 4 during the machining of the core blocks, causing the product yield to decrease.